Sutekh's Earth in 1980

Eager to get away from Sutekh and his minions in 1911, Sarah asks the Doctor to go back to her home time of 1980. The Doctor states that Sutekh will destroy the world if left to his own devices, which Sarah disbelieves, since if the world was destroyed in 1911, she wouldn't exist. The Doctor proves her wrong by taking her to an alternate version of 1980 in which Earth is a desolate wasteland, explaining that Sutekh is so powerful that he can circumvent the laws of time. After seeing what would become of her home planet -- and herself -- if Sutekh isn't stopped, Sarah agrees to go back to 1911 and stop him.

Example of:
Bad Future